WO2020143480A1

WO2020143480A1 - Magnetic core, electric motor having magnetic core, and mower having electric motor

Info

Publication number: WO2020143480A1
Application number: PCT/CN2019/129260
Authority: WO
Inventors: 张涛; 储俊杰; 李敏; 马全同
Original assignee: 广东德昌电机有限公司
Priority date: 2019-01-10
Filing date: 2019-12-27
Publication date: 2020-07-16
Also published as: CN111431304A; US20220085673A1; EP3896824A1; EP3896824A4

Abstract

Disclosed is a magnetic core, comprising an annular body portion, and several magnetic pole portions connected to the body portion. The several magnetic pole portions are distributed on an inner surface of the body portion in a circumferential direction. The body portion is connected to the magnetic pole portions. Each of the magnetic pole portions is in the shape of a triangle and comprises a top end and two free ends. The top end is connected to the body portion. Two side faces, located on two sides of the top end, of each of the magnetic pole portions are respectively opposite and spaced apart from the inner surface of the body portion to form a first accommodating groove and a second accommodating groove. The first accommodating groove and the second accommodating groove are used for housing magnets, and the first accommodating groove and the second accommodating groove are located at an opening end of an inner surface of the magnetic core. The magnetic core of the present invention has a remarkable magnetizing effect and facilitates improving the power density of an electric motor.

Description

Magnetic core, motor with the magnetic core and lawn mower with the motor

Technical field

The invention relates to the field of motors, in particular to a magnetic core, a motor with the magnetic core, and a lawn mower with the motor.

Background technique

Existing motors generally include a stator and a rotor that can rotate relative to the stator. The stator includes a stator magnetic core, an insulating frame sleeved on the stator magnetic core, and a winding wound on the insulating frame. The rotor includes a rotating shaft, a casing fixed on the rotating shaft, and a permanent magnet fixed on the casing. How to improve the motor power density is the goal that has been pursued in this field.

technical problem

In view of this, the present invention aims to provide a high power density motor and its magnetic core, and a lawn mower having the motor.

Technical solution

To this end, one aspect of the present invention provides a magnetic core, including a ring-shaped body portion and a plurality of magnetic pole portions connected to the body portion, the plurality of magnetic pole portions arranged circumferentially on the inner surface of the body portion, characterized in that : The body part and the magnetic pole part are connected to each other, each of the magnetic pole parts is triangular, including a top end and two free ends, the top end is connected to the body part, and the magnetic pole part is located on both sides of the top end A first accommodating groove and a second accommodating groove are formed opposite to and spaced from the inner surface of the body portion. The first accommodating groove and the second accommodating groove are used to accommodate magnets. The inner surface of the magnetic core has an open end.

In some embodiments, the inner surface of the body portion continues to extend in an inverted V shape, the inner surface of the body portion forms alternately arranged peaks and valleys, and the top of each magnetic pole portion is connected by a The part is connected with a corresponding valley part of the body part.

Further, the inner surface of the body portion forms a first inner side surface and a second inner side surface on each side of each valley portion, and the two side surfaces of each magnetic pole portion are respectively connected to the first inner side surface and the second The inner side faces the first accommodating groove and the second accommodating groove at opposite intervals, wherein the included angle between the first inner side and the second inner side is an obtuse angle.

In some embodiments, the first receiving groove and/or the second receiving groove are rectangular, and the first receiving groove and/or the second receiving groove further extend near the top end of the magnetic pole portion Form a recess.

In some embodiments, the body portion protrudes radially inward at the peak to form a limit protrusion, the limit protrusion is located in the first receiving groove and the second receiving groove away from the main portion The outer end.

In some embodiments, an opening is formed between adjacent free ends of two adjacent magnetic pole portions, and the width of the opening is 3 to 5 mm.

In some embodiments, the magnetic pole portion forms a pole face between two free ends, and the pole face has a polar arc degree of 125°.

On the other hand, the present invention also provides a motor including a stator and a rotor rotatable relative to the stator. The rotor includes the aforementioned magnetic core and magnets accommodated in the first and second accommodating slots of the magnetic core .

Further, the housing includes a side wall extending from a periphery of the bottom plate, the side wall includes a bottom end side wall, an intermediate side wall, and a top side wall, the bottom end side wall and the intermediate side wall form a first A step surface, a second step surface is formed between the top side wall and the middle side wall, the first step surface and the second step surface are opposite and spaced apart, and form a common shape with the middle side wall An installation cavity in which the magnetic core is accommodated.

In yet another aspect, the present invention also provides a lawnmower, including a lawnmower body and the aforementioned motor, the motor being installed in the body of the lawnmower.

Beneficial effect

The magnetic pole portion in the present invention is generally triangular, so the first and second accommodating grooves together form a substantially V-shaped structure, so that after the magnet is placed in the first and second accommodating grooves, the corresponding pole face of the magnetic pole portion It can be magnetized into a magnetic pole. The magnetic poles set in this way have a significant magnetic concentration effect, which helps to improve the power density of the motor.

BRIEF DESCRIPTION

FIG. 1 is a structural block diagram of a lawnmower according to an embodiment of the present invention.

Fig. 2 is a perspective view of the motor of the lawnmower shown in Fig. 1.

3 is a cross-sectional view of the motor shown in FIG. 2.

Fig. 4 is an exploded view of the motor shown in Fig. 2.

Fig. 5 is an exploded view of the stator of the motor shown in Fig. 4.

6 is an exploded view of the rotor of the motor shown in FIG.

7 is an exploded view of the rotor core and magnet of the rotor shown in FIG. 6.

8 is a plan view of the rotor core shown in FIG. 7.

9A is a side view of the rotor of the motor shown in FIG. 4.

9B is a cross-sectional view of the rotor shown in FIG. 9A taken along the line A-A.

FIG. 9C is a partial enlarged view at M of the cross-sectional view of the rotor shown in FIG. 9B.

Fig. 10A is a side view of the housing of the rotor shown in Fig. 9A.

10B is a cross-sectional view of the housing shown in FIG. 10A taken along the line B-B.

FIG. 10C is a partially enlarged view at position N of the cross-sectional view of the housing shown in FIG. 10B.

Embodiments of the invention

The present invention will be described in detail below in conjunction with the accompanying drawings and specific embodiments, so that the technical solutions and beneficial effects of the present invention are more clear. It can be understood that the drawings are provided for reference and explanation only, and are not intended to limit the present invention. The dimensions shown in the drawings are only for clear description and do not limit the proportional relationship.

Referring to FIG. 1, a lawnmower according to an embodiment of the present invention includes a lawnmower body 10 and a motor 20 installed in the lawnmower body 10. Since the main improvement of the present invention lies in the motor 20, the conventional structure and principle of the lawn mower body 10 can be used. Therefore, the specific structure of the lawn mower body 10 will not be described in detail in this embodiment.

2 to 4, the motor 20 includes a stator 30 and a rotor 60 disposed substantially around the stator 30. A receiving space 61 is provided in the rotor 60 for receiving the stator 30, and the rotor 60 can rotate relative to the stator 30.

Referring to FIG. 5 at the same time, the stator 30 includes a stator magnetic core 40, an insulating frame 50 sleeved on the stator magnetic core 40, and a winding (not shown) wound on the insulating frame 50. The stator core 40 includes an annular portion 41 at the center and a plurality of tooth portions 42 that are formed to extend radially outward from the outer portion of the annular portion 41. A through hole 410 is formed in the annular portion 41, and the diameter of the through hole 410 is larger than the diameter of the rotating shaft 90, so that the rotating shaft 90 passes through and rotates freely relative to the stator core 40. Each tooth 42 includes a tooth body 420 and a pole shoe 421 provided at the end of the tooth body 420. In this embodiment, the tooth body 420 has a rectangular parallelepiped shape, and the pole shoe 421 extends along the circumferential direction and is substantially arc-shaped. Specifically, the outer surface of the pole shoe 421 is an arc-shaped pole surface, and the inner surface includes two planes distributed on both sides of the tooth body 420 and inclined at an obtuse angle relative to the tooth body 420. Preferably, the plurality of pole shoes 421 are evenly distributed along the circumferential direction, and the outer surfaces of all the pole shoes 421 are located on the same cylindrical surface. The insulating frame 50 includes an annular upper flange 51, an annular lower flange 52, a number of frame-shaped frames 53 connected between the bottom end of the upper flange 51 and the top of the lower flange 52, and connected to the frame-shaped frame 53 The arc-shaped frame 54 at the end, wherein the frame-shaped frame 53 is used to accommodate the tooth body 420 of the stator core 40, and the arc-shaped frame 54 is used to accommodate the pole shoe 421 of the stator core 40. When the insulating frame 50 is assembled on the stator core 40, the outer surface and part of the upper and lower end surfaces of the annular portion 41 of the stator core 40 and the surface of the tooth portion 42 are covered by the insulating frame 50, and the outer surface of the pole shoe 421 It is exposed to ensure that the winding is insulated from the stator core 40 after winding the winding. The material of the insulating frame 50 is preferably plastic.

The structure of the rotor will be described in detail below with reference to FIG. 6. The rotor 60 includes a housing 70, a rotor magnetic core 80 and a rotating shaft 90 fixedly connected to the housing 70, and a magnet 100 fixed in the rotor magnetic core 80. Wherein, the housing 70 is substantially in the shape of a hollow cylinder with one end open, and includes a circular bottom plate 71 and a side wall extending vertically from the periphery of the bottom plate 71. The rotor core 80 is substantially ring-shaped and fixed in the side wall of the housing 70, and the stator 30 is located in the rotor core 80. One end of the rotating shaft 90 is fixed to the center of the bottom plate 71 of the housing 70, and the other end penetrates the stator 30 and protrudes from the opening of the side wall of the housing 70 as an output end.

Also refer to Figures 7-8. In this embodiment, the rotor core 80 includes a substantially ring-shaped body portion 81 and a plurality of magnetic pole portions 82 connected to the body portion 81. The plurality of magnetic pole portions 82 are circumferentially distributed inside the body portion 81 and are connected to the body portion 81 connection. Preferably, the rotor core 80 is formed by stacking several layers of laminations, and each lamination is integrally formed by stamping and forming, and includes a body portion 81 corresponding to a layer and a magnetic pole portion 82 corresponding to a layer. Therefore, after stacking several laminations, the body portion 81 and the magnetic pole portion 82 can be formed. In this embodiment, the number of magnetic pole portions 82 is ten. Both the body portion 81 and the magnetic pole portion 82 are made of ferromagnetic materials, and the ferromagnetic materials may be commonly used iron, cobalt, nickel or alloys thereof. Preferably, both the body portion 81 and the magnetic pole portion 82 are made of soft ferromagnetic materials to improve the magnetic permeability.

The outer surface 810 of the body portion 81 is a cylindrical surface, and the inner surface includes a plurality of V-shaped grooves, so that peak portions 811 and valley portions 812 are alternately arranged on the inner surface. Specifically, each valley portion 812 has first and second inner sides 813 and 814. The angle between the first inner side 813 and the second inner side 814 is an obtuse angle. Preferably, the first and second inner sides 813 and 814 of the body portion 81 are both flat.

Each magnetic pole portion 82 forms a connection with the body portion 81 at a corresponding valley portion 812. In this embodiment, each magnetic pole portion 82 is substantially triangular, and its apex position protrudes radially outward to form a connecting portion 85, and then through the connecting portion 85, the apex of the magnetic pole portion 82 and the corresponding valley portion 812 of the body portion 81 In connection, the two side surfaces on both sides of the apex are spaced apart from the first inner side surface 813 and the second inner side surface 814 on both sides of the valley portion 812 of the body portion 81 respectively, thereby forming slits with open ends on both sides of the magnetic pole portion 82. The radially inner side opposite to the vertex faces the center of the magnetic core and constitutes the pole face of the magnetic core. The pole faces of the magnetic pole portions 82 are located on a circumferential surface that is concentric with the body portion 81.

Specifically, the magnetic pole portion 82 includes a connection end 820, a first free end 821, and a second free end 822. The first outer side 823 of the magnetic pole portion 82 is formed between the connecting end 820 and the first free end 821, and the second outer side 824 of the magnetic pole portion 82 is formed between the connecting end 820 and the second free end 822. A pole face 825 of the magnetic pole portion 82 is formed between the ends 821 and 822. The connecting end 820 is connected to a corresponding valley portion 812 of the body portion 81, and the first outer side surface 823 of the magnetic pole portion 82 is opposed to the first inner side surface 813 on the side of the corresponding valley portion 812 and is spaced apart to form a first A receiving groove 826 in which the first free end 821 of the magnetic pole portion 82 is adjacent to the peak portion 811 on the valley portion 812 side and spaced from each other. Therefore, the first accommodating groove 826 starts at the junction of the valley 812 and the connecting end 820, ends at the first free end 821 and the corresponding peak 811, and forms an opening at the first free end 821 and the peak 811 . The second outer side surface 824 of the magnetic pole portion 82 and the second inner side surface 814 on the other side of the corresponding valley portion 812 form a second accommodating groove 827 for accommodating the magnet 100, wherein the second free end 822 of the magnetic pole portion 82 and the valley portion The peaks 811 on the other side of the 812 are adjacent and spaced from each other. Therefore, the second receiving groove 827 starts at the junction of the valley 812 and the connection end 820 and ends at the second free end 822 and the corresponding peak 811, And an opening is formed at the second free end 822 and the peak portion 811.

The magnet 100 is accommodated in the accommodating grooves 826, 827 formed between the magnetic pole portion 82 and the body portion 81, wherein the magnets 100 accommodated in the first and second accommodating grooves 826, 827 corresponding to each magnetic pole portion 82 have the same polarity . Since the first and second outer side surfaces 823 and 824 of the magnetic pole portion 82 forming the first and second receiving grooves 826 and 827 extend from the connecting end 820 to both sides, the first and second receiving grooves 826 and 826 827 is roughly V-shaped. Preferably, the first and second outer side surfaces 823 and 824 of the magnetic pole portion 82 are also flat and parallel to the first and second inner side surfaces 813 and 814 of the body portion 81, that is, the first and second receiving grooves 826 The axial section of 827 is roughly rectangular.

In this embodiment, the body portion 81 and each magnetic pole portion 82 form first and second receiving grooves 826, 827 for receiving the magnets 100 of the same polarity, and the first and second receiving grooves 826, 827 together constitute a substantially V The shape of the structure is such that after the magnet 100 is embedded in the first and second receiving grooves 826 and 827, the pole face 825 of the corresponding magnetic pole portion 82 is magnetized into one magnetic pole. The magnetic poles provided in this way can significantly improve the magnetic concentration effect, thereby increasing the power density of the motor 20.

Preferably, the degree γ of the polar arc of the magnetic pole part 82 (that is, the arc spanned by the pole face in the circumferential direction) is preferably 125°. This setting can further optimize the magnetic concentration effect of the magnetic pole. Understandably, in other embodiments, the polar radians may also be other obtuse angles.

Preferably, an opening 828 with a width of 3 to 5 mm is formed between the first free end 821 of the magnetic pole portion 82 and the second free end 822 of the adjacent magnetic pole portion 82. As a result, a larger magnetic resistance can be generated, thereby reducing or avoiding the passage of magnetic flux through the opening 828, so that the magnetic flux generated by the magnet 100 located in the first and second receiving grooves 826, 827 passes through the pole face 825 as much as possible. It helps to further improve the magnetic concentration effect, and thus improve the power density of the motor 20. Since the magnetic pole focusing effect in this embodiment is better than the prior art, therefore, in some applications, low-grade neodymium magnets (NdFeB) can be used, thereby reducing the manufacturing cost of the motor 20.

Preferably, the first and second accommodating grooves 826 and 827 further extend to form first and second concave portions 830 and 831 at the connection end 820 adjacent to the magnetic pole portion 82. The first and second recesses 830, 831 are generally in a groove shape with one side open, so that the connecting portion 85 between the body portion 81 and the magnetic pole portion 82 is generally strip-shaped, and the first and second recesses 830, 831 are respectively Located on both sides of the connection portion 85. Preferably, a limiting protrusion 832 is formed at the peak portion 811 of the body portion 81 to project radially inwards, and the limiting protrusion 832 is located at one end of the first and second accommodating grooves 826 and 827 away from the outer surface 810 of the body portion 81. The limiting protrusion 832 can effectively prevent the magnet 100 accommodated in the accommodating grooves 826 and 827 from coming out. In this embodiment, the limiting protrusion 832 corresponds to the opening 828 between the magnetic pole portions 82 one-to-one.

In this embodiment, the housing 70 of the rotor 60 is preferably integrally formed by injection molding. The bottom plate 71 includes a base 72 at the center, a plurality of radially extending ribs 73 connecting the base 72 and the bottom end of the side wall of the housing 70. Preferably, the bottom plate 71 further includes an annular rib 74 connected to the middle of each rib 73, which helps to improve the overall strength of the bottom plate 71.

The rotating shaft 90 is fixedly connected to the bottom plate 71 of the housing 70 through a mounting frame 75 arranged in the base 72. The mounting bracket 75 is embedded in the base 72, and the rotating shaft 90 is directly fixed on the mounting bracket 75. The material strength of the mounting bracket 75 is greater than the material strength of the base 72, so it can provide a stronger support for the rotating shaft 90 and ensure the coaxiality of the rotating shaft 90 and the stator 30 when the rotor 60 rotates. Preferably, the mounting bracket 75 is made of a metal material, and the base 72 is made of plastic. Also preferably, the mounting bracket 75 is integrally embedded into the base 72 by insert molding. In order to clearly show the structure of the mounting bracket 75, the mounting bracket 75 and the base 72 are in a separated state in FIG. 6, but it can be understood that, in the finished motor of the present invention, the mounting bracket 75 may be non-detachable from the base 72 connected. In this embodiment, the mounting bracket 75 and the base 72 each have a through hole 752, 720. The inner diameter of the through hole 752 of the mounting bracket 75 is smaller than the inner diameter of the through hole 720 of the base 72. Preferably, one end of the rotating shaft 90 and the mounting bracket The through hole 752 in 75 has an interference fit.

Specifically, in this embodiment, the mounting bracket 75 includes an annular mounting ring 750 and a plurality of protrusions 751 formed radially outward from the outer circumference of the mounting ring 750. The protrusions 751 of the mounting frame 75 are evenly arranged in the circumferential direction. When the mounting bracket 75 is embedded in the base 72 by insert molding, the material of the base 72 fills the gap between the protrusions 751 of the mounting bracket 75, which helps to improve the torsion of the mounting bracket 75 and the base 72 The strength prevents the mounting bracket 75 from rotating relative to the base 72, thereby preventing the rotating shaft 90 from rotating relative to the housing 70.

The side wall of the housing 70 includes a bottom end side wall 76, a middle side wall 77, and a top side wall 78 that are sequentially connected and whose outer diameter gradually increases. The inner diameter of the bottom end side wall 76 is smaller than the inner diameter of the middle side wall 77, and then an annular first step 770 extending radially is formed between the bottom end side wall 76 and the middle side wall 77. In other words, the first step 770 is located between the outside of the bottom end side wall 76 and the inside of the middle side wall 77. An annular second step 771 extending in a radial direction is formed between the top side wall 78 and the middle side wall 77. Preferably, the inner side of the second step 771 extends radially inward to the same inner diameter as the first step 770. The first step 770 and the second step 771 are opposite to each other, and together with the middle side wall 77 enclose a mounting cavity 772 for accommodating the rotor core 80.

Preferably, a connecting ring 84 is connected between the top of the rotor core 80 and the housing 70. The connection ring 84 can be fixedly connected to the rotor core 80 and the housing 70 by snap-fitting, respectively, and then fixedly connect the housing 70 and the rotor core 80. For example, an inner protrusion 833 may be provided at the top of each magnetic pole portion 82, and an outer protrusion 834 may be provided at the top of the body portion 81 between adjacent magnetic pole portions 82. The connecting ring 84 is provided with inner and outer through holes 840, 841 for passing the inner and outer bumps 833, 834, and the rotor core 80 and the rotor core 80 are realized by the snap fit of the bumps 833, 834 and the through holes 840, 841. Connection of the connecting ring 84. Referring to FIGS. 9A to 10C at the same time, a strip-shaped protrusion 773 is provided at the bottom end of the second step 771 of the housing 70, and a through hole 842 for the protrusion 773 to pass through is provided on the connecting ring 84. The snap fit of the hole 842 realizes the connection between the housing 70 and the connecting ring 84, and further realizes the fixed connection between the housing 70 and the rotor core 80. In this embodiment, the connecting ring 84 is further provided with a notch 843 corresponding to the opening 828 between adjacent magnetic pole portions 82.

In the present embodiment, the housing 70 and the rotor core 80 are integrally non-detachable by overmolding. Specifically, when molding the housing 70, the rotor core 80 (and/or the mounting bracket 75) is arranged in the mold, and plastic is injected into the mold to form the housing 70. In order to enhance the connection strength between the housing 70 and the rotor core 80, the housing 70 further includes a plurality of connecting bars 774 distributed in the mounting cavity 772 in the circumferential direction. The connecting bars 774 are from the bottom end of the second step 771 (that is, facing the first One end of the step 770) penetrates the rotor core 80 axially and is inserted into the first step 770. Preferably, each magnetic pole portion 82 corresponds to two connecting bars 774, and the two connecting bars 774 respectively insert into the first concave portion 830 and the second concave portion 831. Preferably, the housing 70 further includes a plurality of fixing posts 775 distributed in the installation cavity 772 in the circumferential direction. Each fixing post 775 extends in the axial direction, one end is fixedly connected to the top end of the first step 770, and the other end is fixedly connected to the bottom end of the second step 771. The fixing post 775 is embedded in the notch 843 of the connection ring 84 and the opening 828 of the rotor core 80.

The above is only a preferred specific embodiment of the present invention, and the scope of protection of the present invention is not limited to the above-listed embodiments. Any person familiar with the technical field in the technical scope disclosed in the present invention can clearly obtain the technology Simple changes or equivalent replacements of the solutions fall within the protection scope of the present invention.

Claims

A magnetic core includes a ring-shaped body portion and a plurality of magnetic pole portions connected to the body portion, the plurality of magnetic pole portions are arranged on the inner surface of the body portion along the circumferential direction, characterized in that: the body portion and the magnetic pole portion Connected to each other, each of the magnetic pole portions is triangular, including a top end and two free ends, the top end is connected to the body portion, the two side surfaces of the magnetic pole portion located on both sides of the top end are opposite to the inner surface of the body portion and A first accommodating groove and a second accommodating groove are formed at intervals, the first accommodating groove and the second accommodating groove are used for accommodating magnets, and the first accommodating groove and the second accommodating groove have openings on the inner surface of the magnetic core end.
The magnetic core according to claim 1, wherein the inner surface of the body portion includes a plurality of V-shaped grooves spaced apart from each other, thereby forming alternately arranged peaks and valleys on the inner surface, each of the The top end of the magnetic pole part is connected to two adjacent valley parts of the body part through a connecting part.
The magnetic core according to claim 2, wherein each valley portion includes a first inner side surface and a second inner side surface, and the two side surfaces of each magnetic pole portion are respectively connected to the first inner side surface and the second inner side The side surfaces are opposed and spaced apart to form the first receiving groove and the second receiving groove, wherein the included angle between the first inner side surface and the second inner side surface is an obtuse angle.
The magnetic core according to claim 3, wherein the first accommodating groove and/or the second accommodating groove further extend to form a concave portion near the top end of the magnetic pole portion.
The magnetic core according to claim 2, wherein the body portion protrudes radially inward at the peak to form a limit protrusion, the limit protrusion is located in the first receiving groove and the The second accommodating groove is away from the outer end of the main part.
The magnetic core according to claim 1, wherein an opening is formed between adjacent free ends of two adjacent magnetic pole portions, and the width of the opening is 3 to 5 mm.
The magnetic core according to claim 1, wherein the magnetic pole portion forms a pole face between two free ends, and the pole arc degree of the pole face is 125°.
A motor includes a stator and a rotor rotatable relative to the stator, wherein the rotor includes the magnetic core according to any one of claims 1 to 7 and a first accommodating groove accommodated in the magnetic core and The magnet in the second receiving slot.
The motor according to claim 8, wherein the rotor further includes a housing, and the magnetic core is received in the housing, the housing includes a bottom plate and a side wall extending from a periphery of the bottom plate, The side wall includes a bottom end side wall, a middle side wall, and a top side wall, the bottom end side wall and the middle side wall form a first stepped surface, and the top end side wall and the middle side wall are formed A second stepped surface, the first stepped surface and the second stepped surface are opposed and spaced apart, and together with the middle side wall form a mounting cavity, and the magnetic core is accommodated in the mounting cavity.
A lawnmower, characterized by comprising a lawnmower body and a motor according to claim 8, the motor being installed in the lawnmower body.